Diodes, transistors and other power control devices are an indispensable part of the manufacturing, environmental, transportation and communications systems that we have come to rely upon. Dozens of such devices are often needed within even the simplest of such systems.
While such devices are important in their current form, there is an ever increasing need to further reduce the size and power consumption of such devices. However, as the size decreases, the materials used in the construction of such devices must be adapted to meet the ever increasing electrical and thermal stress caused by the reduced size.
One promising material to meet the needs of future integrated circuits is silicon-carbide (SiC). SiC has been recognized as being the material of choice for future system.
In order to justify the migration to SiC, processes must be developed that exploit the relatively high voltage and current carrying capabilities of SiC. However, due to very poor diffusion of impurities in SiC, well-established techniques used for prior-art silicon devices can not be adapted to SiC. For example, one reference describes a mesa-type structure created by a dry etching technique where difficulties associated with edge termination are reduced by etching away the junction and depositing a passivation layer over the junction. While mesa termination by dry etching is simple, it has been unsuccessful because it suffers from edge leakage and, ultimately, edge failure at a reverse voltage that is far less than the ideal value that SiC is capable of withstanding.
Other efforts have relied upon the creation of field rings and junction termination extension regions disposed on a surface of the diode. However, field rings and junction termination extension regions may require implantation and diffusion, which is difficult for SiC. Further, the use of junction termination extension regions on the diode surface results in surface damage and leakage.
Another reference has described a three-step termination scheme using a junction termination extension. However, the p+ anode of the reference was still formed by ion implantation. Further, the use of the three-step termination scheme is complicated and requires accurate control of etch depth.
In general, all known techniques require either high energy implants that damage the SiC surface, or subject the high electric field regions to contamination and defects. Each of these techniques create the risk of defect related failure and excessive leakage current through the high electric field regions. Accordingly, a need exists for better methods to fabricate SiC devices.